Fig. 1

New cases of syphilis detected by eliciting in-person connections (red boxes). Syphilis status is coded by the color of vertices: red vertices tested positive for syphilis, and blue vertices tested negative for syphilis. Cases of syphilis that were detected due to asking for social ties are shown in red boxes. Squares are males, and circles are females. Green edges are social connections, and black edges are sexual connections. Arrows point from nominated individuals to index cases